Conventionally, there has been known a liquid crystal optical element that utilizes the birefringence of a liquid crystal molecule and applies a voltage to the liquid crystal molecule to change a refractive index distribution. Furthermore, there has been proposed a stereoscopic image display device that is constituted by combining the liquid crystal optical element and an image display module.
In the above-mentioned stereoscopic image display device, the refractive index distribution of the liquid crystal optical element is changed between a state in which an image displayed on the screen of the image display module is made incident on the eyes of a viewer as it is and a state in which the image displayed on the screen of the image display module is made incident on the eyes of the viewer as a plurality of parallax images. Due to such a constitution, a two-dimensional display operation and a three-dimensional image display operation are realized. Furthermore, there has been known a technique for utilizing the optical principle of a Fresnel zone plate to change the optical path of light.
However, in the above-mentioned conventional art, the controllability of the liquid crystal molecule is not considered particularly and hence, there exists a case that it becomes difficult to realize the intended refractive-index-distribution characteristics of a lens. In this case, it is impossible to obtain desired condensing performance thus giving rise to a drawback that image quality in displaying a stereoscopic image is deteriorated.